1. Field of the Invention
This invention relates to a method for the production of substrates with a uniform dispersion of extremely fine granules.
2. Description of the Prior Art
A gas-evaporation technique, in which a metal semiconductor or a dielectric is heated causing evaporation of extremely fine granules onto a supporter in an inert gas atmosphere at low pressure (e.g., from 0.1 to 10 Torrs), resulting in a substrate on which extremely fine granules are dispersed, is well known. The substrate formed by the above-mentioned method is used as a base for the production of a medium for magnetic recording in the field of information processing, the production of catalysts in chemistry, the production of various kinds of sensor materials, and the production of electric circuit devices such as switch devices, memory devices, diodes, etc.
However, when this method is used, generally speaking, several or several tens of extremely fine granules are recovered in a coupled form, and it is not possible to obtain uniform dispersion with minute spaces between the granules on the supporter. The reason for this phenomenon is as follows: In this method, the extremely fine granules, which are formed in the gas with diameters ranging from tens to thousands of Angstroms, collide repeatedly with gas molecules, so that the kinetic energy of the initial stage is rapidly lost, and the granules are carried by a convection stream of gas, which is caused by the heat of a heat source for the evaporation, and accumulated on the supporter. Thus, the distance in which the granules are in motion in the gas before arriving at the supporter becomes very long. This process of transportation seems to be the cause of the successive aggregations of granules touching each other. When the extremely fine granules are coupled with each other on the supporter, the regions of coupled fine granules become, in effect, regions of large granules, and the physical and chemical characteristics of the extremely fine granules are lost. For that reason, if such a dispersed substrate of extremely fine granules is used, for example, for sensor materials or materials for electronic circuits, the proportion of unsatisfactory production increases, and it is not possible to ensure the production reliability of the electronic parts, etc., constructed using this substrate.